The present invention relates to a container box of a plurality of various wafer materials such as semiconductor silicon wafers, photomask glass plates, liquid crystal cells, recording media and the like for the purpose of storage, transportation or positioning of the wafer materials in mounting and demounting onto and from a processing machine therefor. More particularly, the invention relates to improvements relative to the material of the wafer container box and the mounting structure of various accessory parts of the wafer container box such as robotic flanges, side rails, manual handles and the like.
As a reflection of the very strong requirement for cost reduction of semiconductor devices, semiconductor silicon wafers as a typical class of wafer materials in the electronic industries are now under a continued trend for a rapid shift toward a larger and larger diameter of the wafers reaching or exceeding a diameter of 300 to 400 mm or even larger.
On the other hand, the patterning works to form a circuit pattern on the wafer is under a trend toward higher and higher fineness in order to increase the degree of integration of the semiconductor devices so much. A great increase in the fineness of circuit patterning on a semiconductor wafer cannot be accomplished naturally without upgrading of the cleanness of not only the processing lines and rooms for semiconductor processing but also the wafer container boxes for storage and transportation of the wafer materials before or under processing in an intermediate stage.
As a measure to comply with this requirement for the highest cleanness of the processing environment, a method is proposed in which certain key zones within the processing lines of semiconductor wafers only are kept under the highest cleanness in consideration of the high costs for keeping the highest cleanness over the whole processing lines and the wafer materials under processing are transferred between the key zones as contained in a hermetically sealable wafer container box in order to avoid contamination in the course of transportation. This method can of course be successful only with development of a wafer container box which is suitable for automatic transportation between processing zones and automatic exact loading/unloading of the wafer materials on and from the processing machine without least risks of contamination.
Though not shown by way of illustration, a wafer container box for storage and transportation of wafer materials as well as for loading/unloading of the wafer materials on and from a processing machine in the course of processing has a general structure consisting of a laterally opening body of the container box for holding a plurality of wafer materials in parallel alignment to avoid contacting of adjacent wafers and a covering which hermetically seals the lateral opening of the box body with intervention of an elastic gasket. The opening of the box body is engageable with a processing machine when the container box is set on the machine.
A pair of holding members, which serves to hold a plurality of wafer materials each in a horizontal disposition, are provided on the inside surfaces of oppositely facing side walls. A bottom plate, which may be a raised part equivalent to a bottom plate, is mounted on the bottom of the container box and the bottom plate is provided with a plurality of grooves each having an inversely V-formed cross section, referred to as V-grooves hereinafter, to serve for positioned mounting of the container box on a processing machine and penetrating holes for fixing the container box on a processing machine, referred to as retaining fixtures hereinafter.
A pair of bottom rails run on the bottom surface of the container box along the oppositely facing marginal lines of the bottom surface in the direction from the lateral opening to the rear wall opposite to the lateral opening. Each of the bottom rails is integrally shaped with the box body and the bottom plate. An elastic gasket is interposed between the lateral opening of the box body and the covering to ensure air-tight sealing when the covering is mounted on the opening of the box body. A latch mechanism, which can be operated from outside of the box, is built in the covering and the engagement hook of the latch mechanism is engaged with the lateral opening of the box body to ensure air-tightly sealed condition of the box.
The above mentioned holding members and the bottom plate are shaped separately from the body of the container box and they are fixed to the box body with intervention of an O-ring by means of a metal bolt or an engagement hook. When the wafer container box has to be cleaned by washing, accordingly, a number of these demountable parts are removed prior to washing and, after washing and drying of the box body, they are re-assembled to build up the container box. If washing of the container box is carried out without removing these demountable parts, the cleaning solution is unavoidably retained even by rinse within the narrow interstices between the demountable parts and the box body so that a quite long time is taken for complete drying of the washed box body.
Though not shown by drawings, wafer processing machines in general are equipped with a load port for mounting a wafer container box while a plurality of positioning pins having a semispherical end point and a means for fixing the wafer container box are provided on the upper surface of the load port. Accordingly, the wafer container box is positioned in place on the processing machine by a plurality of V-grooves and fixed to the position by means of the retaining fixture.
When wafers are to be processed by utilizing the above described assembly of apparatuses, the latch mechanism of the covering is first brought to disengagement so as to free the engagement hook from the engagement hole in the front of the container box enabling demounting of the covering which is in a position to close the front opening of the container box. Once the covering has been removed, the wafer materials mounted on the loading boat are taken out one by one from the container box and introduced into the processing machine where the wafer materials are processed.
In the current manufacturing process of semiconductor devices, proposals are made for preventing contamination of wafer container boxes by means of automatic transportation of the wafer container boxes in place of conventional manual transportation by the workers. The actual methods for the automatic transportation of wafer container boxes include the OHT (overhead hoist transportation) method in which the wafer container box is held at the robotic flange supported the flat plate 30 can be provided with one or more of fixing holes 33 in the areas excepting the end portions guide rail, AGV (automated guided vehicle) method in which the container box is transported under lifting by utilizing a pair of bottom rails provided on the bottom surface of the container box or a pair of side rails protruded out of the opposite side walls of the container box and PGV (person-guided vehicle) method. Besides, a method called the RGV (rail guided vehicle) method is known in which the mechanism for transportation of the wafer contained in the box is something resembling a monorail way.
In addition, an improvement of the manual transportation method by workers is proposed according to which manual handling of the wafer container box is facilitated by providing a pair of handles for grasping on both side walls of the container box body.
While the automatic transportation methods of wafer container boxes in the prior art can be classified into several types, it is usually the case that a particular wafer-processing step requires a specific transportation method selected from these types of the methods. Although the method utilizing a pair of bottom rails and robotic flanges is considered to be most versatile in respect of standardization of the process, this method can hardly be universal for all of the wafer processing steps. In practice, different transportation methods are employed in a single production line of the wafer processing steps in consideration of the specific conditions of the respective lines or the transportation method is necessarily limited to a specific method. It is sometimes the case that a specially designed transportation method not falling within the above described types must be adapted.
For example, while it is necessary in the transportation method utilizing bottom rails that the processing machine is provided on both sides with recessed parts or cavities on both sides for insertion of the pickup hooks of AGV and the like, this is not always possible depending on the structure of the processing machine. An alternative measure for this difficult problem is that, in place of providing side recesses on the processing machine, side rails to be protruded on both side walls of the container box at a height above the bottom on the body of the box rails in order to facilitate picking up of the container box body by means of an AGV and the like and these side rails are utilized for lifting up the box body kept in a horizontal disposition.
When the method of ceiling transportation is adapted by utilizing an OHT which requires that the ceiling height must be sufficiently large for installation of the OHT, it is sometimes a possible case that no space for installation of the OHT is available relative to the height of ceiling, especially, when a transportation mechanism must be introduced into an existing room of an old plant. When the method of ceiling transportation is adapted, in addition, a problem to be taken into consideration is that the robotic flange is provided to have a sufficiently high mechanical strength because the wafer container boxes currently under use may have a weight exceeding 7 kg when loaded with the full number of semiconductor silicon wafers.
In order to comply with each of these different transportation methods with a single type of wafer container boxes, the container box is required to be provided with parts of different structures for transportation. The transportation parts for actual service in a wafer processing plant are limited only to one or two types so that the other parts not in service are not only absolutely extraneous but also very deleterious due to an unnecessary increase in the weight and volume and troubles in handling relative to cleaning and storage.
For example, the robotic flanges and side rails are each a protrusion out of the surface of the box body. Since the side rails are each a protruded body having a protrusion height of 20 mm or larger and integrally molded with the box body, a great inconvenience is unavoidable in wrapping of the wafer container boxes with an aluminum foil-plastic film laminate and polyethylene film or by shrinkable wrapping for transportation and storage because of possible occurrence of pin holes in the wrapping films leading to eventual contamination of the wrapped container boxes. When the wafer processing plant is so designed as not to employ wafer container boxes having protruded side rails formed by integral molding, there may be a risk that the protruded side rails cause interference with other parts of the plant. Needless to say, a larger space must be provided for the cleaning works and storage of such wafer container boxes having protruded side rails corresponding to the volume occupied by the protruded side rails.
It is of course possible that the above mentioned specific parts for transportation are provided in a demountable fashion. While it is a usual way to ensure mechanical strengths of such demountable transportation parts by means of a plurality of screw bolts and nuts, difficulties are encountered in mounting and demounting of the transportation parts by using a so large number of the screw bolts in addition to the problems of an increase in the positioning error sometimes necessitating other special parts for exact positioning. Further, it is also possible to provide the container box with a pair of handles to facilitate manual handling of the boxes. Such handles, however, are useful only in the stage of trial manufacturing, in an emergency and in few of other steps not suitable for automatization such as product inspection and not useful in the routine manufacturing lines being rather obstructive in handling, transportation and storage and disadvantageous in costs.
On the other hand, it is sometimes the case in a part of the manufacturing lines of semiconductor devices that the semiconductor silicon wafers contained in the wafer container box are electrostatically charged at a high potential. A means undertaken to discharge the high-potential electrostatic charges by grounding to the mechanical part such as the load port is to form the supporting members, which are built to the body of the box as separate parts, from an antistatic material having a surface resistivity of 108 ohm to 1013 ohm and the connecting part thereof to the body of the box is electrically connected through a separate electroconductive member to the robotic flanges, V-grooves, side rails or bottom rails equally made from an antistatic material.
Since the body of the wafer container box is made usually from an electrically insulating material which is transparent or translucent in order to ensure see-through visibility of the inside of the box, however, dust particles are unavoidably deposited and adsorbed onto the electrostatically charged surface of the box body under transportation within the production line so that the contaminants are brought into the environment of the wafer-processing sealed zones which must be kept in the highest cleanness resulting in various troubles. Further, the number of parts constituting the wafer container box is necessarily increased along with an increase in the costs for assemblage of parts and cleaning of the box since the box body is provided with electroconductive additive parts such as those having wafer alignment grooves.
The present invention, which has been completed in view of the above described various problems and disadvantages in the prior art wafer container boxes, accordingly has an object to provide a novel and improved wafer container box having adaptability to different ways of transportation by employing parts required for a specifically selected transportation method so as to improve interchangeability, lightness in weight, handleableness and storage performance. Another object of the invention is to provide a wafer container box on which the problem of dust particle deposition can be minimized even by the use of an electrically insulating transparent material to ensure see-through visibility for inspection of the inside of the box.
Thus, the present invention provides a wafer container box consisting of a body of the box opening in one lateral surface and a covering mountable on the opening of the box body for air-tight sealing of the container box, which comprises:
(a) two sets of wafer alignment grooves each integrally formed on the inner surface of one of oppositely facing side walls of the box body for supporting a plurality of wafer materials aligned up to down each in a horizontal disposition;
(b) a bottom plate fixed to the bottom surface of the box body;
(c) an upper mounting means provided on the top wall of the box body for supporting a robotic flange in a demountable fashion;
(d) a lower side mounting means provided on the outer surface of each of the side walls of the box body for supporting a side rail in a demountable fashion; and
(e) a side mounting means provided on the outer surface of each of the oppositely facing side walls of the box body for supporting a manual handle in a demountable fashion, wherein the members selected from the robotic flanges, side rails and handles are supported selectively.
Characteristically, the above mentioned upper mounting means (c) comprises a guide rail provided on the top wall of the box body and an inclined guide surface formed in the guide rail with inclination gradually increasing from the end surface opposite to the lateral opening toward the lateral opening, and the robotic flange comprises a holding plate and supporting props provided on the lower surface of the holding plate to fit the guide rails as guided by the inclined guide surface.
Further characteristically, the above mentioned lower mounting means is formed in the form of an engagement rib provided on the outer surface of each side wall so as to define a space for insertion and the above mentioned side rail comprises a flat plate, an insertion part provided on the inward end of the flat plate for engagement with the engagement rib and a horizontal supporting plate provided on the outward end of the flat plate.
Still more characteristically, the above mentioned side mounting means comprises a guide rail provided on the outer surface of each side wall of the box body and an inclined guide surface with inclination gradually increasing from the end surface of the box body opposite to the opening toward the opening and the manual handle is constituted from a plate fitting the guide rail as being guided by the above mentioned inclined guide surface and a handle provided on the outer surface of the plate.